The invention refers to an automatic analyzer for the assay of liquid samples.
Automatic analyzers for the analysis of liquid samples of biological substances such as blood or urine are well known. FIG. 1 schematically shows the block diagram of a prior art automatic analyzer 10. Samples are provided in separate containers, e.g. on an array 11. By means of an automatic pipetting device 12, small amounts of the samples are transferred to a mixing chamber 14 in a serial manner. Chamber 14 is an upwardly open reaction cuvette connected to inlet openings 15 and 16 for air and water, respectively, to homogenize the respective liquid sample in order to rinse the chamber. Excess liquid or washing liquid (waste) may be evacuated through a first outlet opening 17. Through a second outlet opening, i.e. a connecting tube 21, the diluted liquid sample is supplied to the measuring channel of a block of electrodes 22 which allows measurement of the concentration of ions, e.g. Li+, K+, Na+, Clxe2x88x92, by means of ion-selective electrodes. Finally, the liquid sample is discharged through an outlet 23 for destruction.
The described arrangement is associated with a comprehensive electronic control, surveillance, and evaluation system 24 which controls and monitors the pipetting operations for taking samples from the sample containers of array 11 and for transferring each of the samples to a reaction cuvette of a mixing chamber 14. This electronic control system comprises program-controlled microprocessors.
The operation of automatic analyzers of the kind represented in FIG. 1 should be as trouble free as possible. However, for various reasons, this aim can only be attained within certain limits. In particular, frequent problems are caused by small particles such as blood clots which may choke the pipetting needle and other parts of the analyzer, thereby resulting in analysis errors or even rendering the measurements impossible. Therefore, it is desirable to provide devices to monitor the pipetting operations as effectively as possible. This can be achieved by monitoring the pressure values during aspiration and ejection of the liquid samples into and out of the pipetting needles, respectively. Attempts of this kind are known from WO 95/00829, U.S. Pat. No. 4,794,085, EP-A-0 289 946, and EP-A-0 210 014.
Another known monitoring device is related to controlling an accurate immersion depth of the tip of the pipetting needle into the liquid sample. Such control is necessary when the sample liquids contained in the sample containers of array 11 have different level heights. For instance, references U.S. Pat. No. 5,493,922, EP-A- 0 694 784, U.S. Pat. Nos. 5,012,683, and 4,326,851 describe known devices for controlling the immersion depth of the tip of the pipetting needle into a liquid sample. A known control device of this kind uses a high frequency field for that purpose.
Other methods involving use of optical means for controlling the immersion depth of the tip of the pipetting needle are also known.
In view of the foregoing, the aim of the present invention is to provide an automatic analyzer which allows highly effective monitoring of pipetting operations. This means that the number of failures and measuring errors are far lower than in comparable analyzers of the prior art. This results in a substantial reduction of operating time losses and improved accuracy and reliability of measurement results.
According to the present invention, this aim is achieved by an automatic analyzer comprising:
a pipetting device for removing the liquid sample from a container and for transferring the sample,
a mixing chamber having a reaction cuvette for receiving the sample,
means for controlling the operation of the analyzer,
sensors for monitoring the function of the analyzer,
means for evaluating possible monitoring results and for delivering possible error messages, whereby the means include at least one program-controlled processor,
a plurality of operation and monitoring control units which are independent from each other,
a central processing unit for activating each of the control units by a start command and for carrying out a process which ends with the delivery of a corresponding mode signal (S1 to S7) to the central processing unit, and
a combinatory logic circuit which is connected to at least two of the control units, the logic circuit combining messages delivered by the control units as a logical AND and delivers to the central processing unit an output mode signal which corresponds to the combinatory result, and
reactions of the analyzer each of which corresponds to each one of the mode signals (S1 to S7) being provided in the central processing unit.
The automatic analyzer of the present invention provides numerous advantages over the prior art. The extended control and monitoring possibilities provided by the automatic analyzer of the invention result in significant improvement of the reliability and accuracy of the operation of the analyzer as previously mentioned.